I don't much care for pornography, but it might be surprising for fair-minded types to note that most Britons don't see it quite that way. Which ought to make politicians think twice about trying to regulate adult pornography, because if being grown up counts for anything, then it must involve some kind of interest in the serious business of sex. But never mind... Ed Vaizey is talking tough on the subject, suggesting that adult pornography should be blocked by internet providers unless hapless consumers "opt in" to see filth on their screens.

We like pornography so much that Enders Research reckons that half of all online video watching is for this sort of entertainment. So rather more people than Vaizey thinks might be caught up in opt-in net. See this graph below to see how we are a nation of porn lovers – if you like figures, you'll love this.

Adult entertainment takes up nearly double the time that YouTube does Public Domain

Then there's the question of defining "adult pornography". This is notoriously difficult. That said, it's safe to assume that you can expect ministers to rule that anything page3.com (and Mail Online) does is all right for general release, while more explicit sites such as YouPorn should be blocked at source. Then you have to ask (in the era of WikiLeaks) whether ISPs should really be entrusted with a list of people who are "porn enabled" versus a list of those that are not. Be kinda embarrassing if that database ever got out.

Next, it is worth remembering that plenty of pornography is already legal, although you have to go the the trouble of reaching for the top shelf to opt-in. Which should make any sane person makes wonder whether blocking access to websites is the way to go. The point that is often made is that the serious seekers of such entertainment can find what they want online, regardless of whether a few sites are blocked – which is why child pornography is so hard to eradicate. But there is a more important argument: whether banning websites is really proportionate.

As Larry Flynt, the Hustler magazine publisher, has pointed out many times, you may not like pornography, but banning it quickly becomes an important freedom of speech issue. We can all agree that child pornography is problematic, but this is an exceptional case. Adult entertainment is really a matter of taste, and its makers usually participate willingly in the creation of the content. Meanwhile, nobody, of course, likes the idea of children stumbling on all sorts of explicit adult video, but these are issues that can be tackled with a mixture of sensible parenting and good parental control software packages that can help.

What it is not obvious that going down a Chinese-government style route of blocking access to certain webservers is really attractive. It is an idea that has also been canvassed by the film and music businesses hoping to deal with the problems of piracy. Filtering out pornographic websites would certainly provide legitimacy to that suggestion, and then you have to ask what else should be banned next? The WikiLeaks website, of course, and perhaps any other website that is involved in leaking/releasing previously confidential information. A nice trinity of national security, piracy and porn.

One final thought: if you think this is an unlikely scenario, then think again. There is a Communications Bill in the offing next year. Ofcom is already saying that this is the moment to debate online content regulation. Or as the regulator puts it: if somebody is offended watching a YouTube video on their full-screen television at home, then they will want to know who (if anybody) they can complain to about it. Yes, the debate about internet content regulation is worth having, but it is a bit early to think about blocking content you may not like. If freedom of speech is worth anything, it has to be defended in the hard cases, not the easy ones.